1. Field of the Invention
The present invention relates to a process for drying aliminoxane and a process for producing polymers, and more particularly, it relates to a process for obtaining aluminoxane which is used as a catalyst in polymerization of polymerizable monomers, in a state suitable for use as a catalyst.
2. Description of the Related Arts
Aluminoxane is usually obtained from an organoaluminum compound such as trialkylaluminum as the starting material, and it results in a solution diluted with a large amount of organic solvents containing unreacted organoaluminum. Accordingly, a drying step for removing said organoaluminum and the organic solvents is required at the last stage. However, if the resulting aluminoxane solution is heated to dryness without any treatment, it evaporates into a glassy solid state, through a state of highly viscous solution. Therein a large amount of power is required to reach such a dryness, and a uniform drying is difficult.
As the catalyst for production of polymers, aluminoxane is desired to be in powder form, which is easy to dissolve. To obtain aluminoxane powder, however, only the spray-drying method and the solvent deposition method have been known.
Said spray-drying method requires a large amount of inert gas, accompanies a considerable amount of aluminoxane losses, and gives a poor yield. The solvent deposition method requires a large amount of solvent, and in addition, another step for removing solvents.
According to these methods, further, the resulting aluminoxane sometimes contains residual trialkylaluminum in a large amount, and it was difficult to obtain an aluminoxane of high quality.